A toroidal continuously variable transmission comprises power rollers between an input disk and output disk, and a rotation of the input disk is transmitted to the output disk via the power rollers. When trunnions supporting the power rollers are displaced vertically in mutually opposite directions by hydraulic actuators, the power rollers incline, and the ratio of the rotation speed of the input disk to the rotation speed of the output disk, i.e., a speed ratio, varies.
Tokkai Hei 2-163562 published by the Japanese Patent Office in 1990 discloses an oil pressure control device of the toroidal continuously variable transmission comprising a first valve and a second valve for operating the actuators which displace the trunnions. The actuators are operated by the first valve during forward running of the vehicle wherein the speed ratio varies widely, and by the second valve during reverse running of the vehicle.